When installing gas lines, water lines, sewer lines and the like, a pipe pusher is typically used to push a series of pipe segments through a generally horizontally extending hole or tunnel below ground level. Each sequentially installed pipe segment is connected to an adjacent pipe segment to form the pipeline. A pipe pusher may also be used to install a piping system inside a preexisting gas, sewer or water lines, in which case the pipe segments are pushed inside the preexisting pipelines. In either case, in order to gain access to the hole in which the pipe is to be installed, a generally vertically extending shaft is excavated down to the elevation of the hole. The shaft is typically circular in diameter, and is large enough to allow workmen and equipment access to the hole.
Once access to the hole is established, various methods may be utilized for pushing the pipe into the hole. For example, a backhoe anchored at ground level may extend into the shaft, and may be manually operated to grip and push the pipe segments into the hole. However, because the backhoe is located remotely from the pipe and must be operated at awkward angles, its efficiency is limited. It is more desirable to utilize a pipe pusher that can be located within the shaft at the same elevation as the installed pipe. In one such embodiment, a reciprocating hydraulic or pneumatic piston/shaft combination is used to push the pipe into the tunnel. However, when the piston of such a pipe pusher is in its withdrawn (retracted) position, substantial clearance is required behind the pipe pusher to accommodate the withdrawn piston. This requires a shaft that is increased is size to accommodate the piston, which adds to the time and expense of the installation operation. In reduce the required space in the shaft, pipe pushers utilizing a variety of ropes, wires, belts, and/or chains and pulleys have been developed that push or pull the pipe into the tunnel. The wire and pulley arrangement eliminates the need for substantial clearance behind the pipe pusher frame. However, the various wires and pulleys are complex to set up and operate, and can bind or become untracked relatively easily.
Furthermore, it often desired change the direction in which the pipe is being pushed. For example, there may be a second hole or tunnel within the shaft that is about 180 degrees apart from the hole into which pipe is being pushed. In order to push pipe in this second hole, most existing pipe pushers must be lifted by a crane and rotated about 180 degrees in the shaft so that the pipe pusher is properly oriented to push pipe in the second hole. However, this process is difficult and time consuming.
Accordingly, there is a need for a pipe pusher which can fit into a shaft and is relatively compact, which is robust and reliable in operation, and which can push pipe in two, opposed directions.